Danish opted out of his deal with the Nationals and is now a free agent, Mark Feinsand of MLB.com reports.
Danish made 32 appearances for the Red Sox last season but has yet to take the ball at the major-league level this season. He's been OK at Triple-A Rochester this year from a run-prevention standpoint (3.72 ERA), but his 1.52 WHIP and 6.2 K/9 tell a different story, showing instead a pitcher walking a fine line.